1. Field of the Invention
The present invention relates to devices and related methods for treating and improving the function of dysfunctional heart valves. More particularly, the invention relates to devices and related methods that passively assist to close a heart valve to improve valve function of poorly functioning valves.
2. Description of the Related Art
Various etiologies may result in heart valve insufficiency depending upon both the particular valve as well as the underlying disease state of the patient. For instance, a congenital defect may be present resulting in poor coaptation of the valve leaflets, such as in the case of a monocusp aortic valve, for example. Valve insufficiency also may result from an infection, such as rheumatic fever, for example, which may cause a degradation of the valve leaflets. Functional regurgitation also may be present. In such cases, the valve components may be normal pathologically, yet may be unable to function properly due to changes in the surrounding environment. Examples of such changes include geometric alterations of one or more heart chambers and/or decreases in myocardial contractility. In any case, the resultant volume overload that exists as a result of an insufficient valve may increase chamber wall stress. Such an increase in stress may eventually result in a dilatory process that further exacerbates valve dysfunction and degrades cardiac efficiency.
Mitral valve regurgitation often may be driven by the functional changes described above. Alterations in the geometric relationship between valvular components may occur for numerous reasons, including events ranging from focal myocardial infarction to global ischemia of the myocardial tissue. Idiopathic dilated cardiomyopathy also may drive the evolution of functional mitral regurgitation. These disease states often lead to dilatation of the left ventricle. Such dilatation may cause papillary muscle displacement and/or dilatation of the valve annulus. As the papillary muscles move away from the valve annulus, the chordae connecting the muscles to the leaflets may become tethered. Such tethering may restrict the leaflets from closing together, either symmetrically or asymmetrically, depending on the relative degree of displacement between the papillary muscles. Moreover, as the annulus dilates in response to chamber enlargement and increased wall stress, increases in annular area and changes in annular shape may increase the degree of valve insufficiency. Annular dilatation is typically concentrated on the posterior aspect, since this aspect is directly associated with the expanding left ventricular free wall and not directly attached to the fibrous skeleton of the heart. Annular dilatation also may result in a flattening of the valve annulus from its normal saddle shape.
Alterations in functional capacity also may cause valve insufficiency. In a normally functioning heart, the mitral valve annulus contracts during systole to assist in leaflet coaptation. Reductions in annular contractility commonly observed in ischemic or idiopathic cardiomyopathy patients therefore hamper the closure of the valve. Further, in a normal heart, the papillary muscles contract during the heart cycle to assist in maintaining proper valve function. Reductions in or failure of the papillary muscle function also may contribute to valve regurgitation. This may be caused by infarction at or near the papillary muscle, ischemia, or other causes, such as idiopathic dilated cardiomyopathy, for example.
The degree of valve regurgitation may vary, especially in the case of functional insufficiency. In earlier stages of the disease, the valve may be able to compensate for geometric and/or functional changes in a resting state. However, under higher loading resulting from an increase in output requirement, the valve may become incompetent. Such incompetence may only appear during intense exercise, or alternatively may be induced by far less of an exertion, such as walking up a flight of stairs, for example.
Conventional techniques for managing mitral valve dysfunction include either surgical repair or replacement of the valve or medical management of the patient. Medical management typically applies only to early stages of mitral valve dysfunction, during which levels of regurgitation are relatively low. Such medical management tends to focus on volume reductions, such as diuresis, for example, or afterload reducers, such as vasodilators, for example.
Early attempts to surgically treat mitral valve dysfunction focused on replacement technologies. In many of these cases, the importance of preserving the native subvalvular apparatus was not fully appreciated and many patients often acquired ventricular dysfunction or failure following the surgery. Though later experience was more successful, significant limitations to valve replacement still exist. For instance, in the case of mechanical prostheses, lifelong therapy with powerful anticoagulants may be required to mitigate the thromboembolic potential of these devices. In the case of biologically derived devices, in particular those used as mitral valve replacements, the long-term durability may be limited. Mineralization induced valve failure is common within ten years, even in older patients. Thus, the use of such devices in younger patient groups is impractical.
Another commonly employed repair technique involves the use of annuloplasty rings. These rings originally were used to stabilize a complex valve repair. Now, they are more often used alone to improve mitral valve function. An annuloplasty ring has a diameter that is less than the diameter of the enlarged valve annulus. The ring is placed in the valve annulus and the tissue of the annulus sewn or otherwise secured to the ring. This causes a reduction in the annular circumference and an increase in the leaflet coaptation area. Such rings, however, generally flatten the natural saddle shape of the valve and hinder the natural contractility of the valve annulus. This may be true even when the rings have relatively high flexibility.
To further reduce the limitations of the therapies described above, purely surgical techniques for treating valve dysfunction have evolved. Among these surgical techniques is the Alfiere stitch or so-called bowtie repair. In this surgery, a suture is placed substantially centrally across the valve orifice between the posterior and anterior leaflets to create leaflet apposition. Another surgical technique includes plication of the posterior annular space to reduce the cross-sectional area of the valve annulus. A limitation of each of these techniques is that they typically require opening the heart to gain direct access to the valve and the valve annulus. This generally necessitates the use of cardiopulmonary bypass, which may introduce additional morbidity and mortality to the surgical procedures. Additionally for each of these procedures, it is very difficult, if not impossible, to evaluate the efficacy of the repair prior to the conclusion of the operation.
Due to these drawbacks, devising effective techniques that could improve valve function without the need for cardiopulmonary bypass and without requiring major remodeling of the valve may be advantageous. In particular, passive techniques to change the shape of the heart chamber and associated valve and/or reduce regurgitation while maintaining substantially normal leaflet motion may be desirable. Further, advantages may be obtained by a technique that reduces the overall time a patient is in surgery and under the influence of anesthesia. It also may be desirable to provide a technique for treating valve insufficiency that reduces the risk of bleeding associated with anticoagulation requirements of cardiopulmonary bypass. In addition, a technique that can be employed on a beating heart would allow the practitioner an opportunity to assess the efficacy of the treatment and potentially address any inadequacies without the need for additional bypass support.
A recently developed passive technique that addresses at least some of the drawbacks discussed above includes applying passive devices to the heart, for example the left ventricle, to change the shape of the ventricle and concomitantly to improve coaptation of the mitral valve leaflets. In one embodiment, the technique involves implanting splints across the left ventricle. Examples of various splinting approaches are disclosed in U.S. application Ser. No. 09/680,435, filed Oct. 6, 2000, entitled xe2x80x9cMethods and Devices for the Improvement of Mitral Valve Function,xe2x80x9d which is assigned to the same assignee as the present application and which is incorporated by reference in its entirety herein.
The devices and related methods which will be disclosed herein also operate passively to treat valve insufficiency, by altering the shape of the valve annulus and/or repositioning the papillary muscles, for example. Some of the devices of the present invention may be used in combination with the splinting treatments disclosed in U.S. application Ser. No. 09/680,435, incorporated by reference herein.
It should be understood that the invention disclosed herein could be practiced without performing one or more of the objects and/or advantages described above. Other aspects will become apparent from the detailed description which follows. As embodied and broadly described herein, the invention includes a method for treating a heart valve comprising providing a device having an arcuate portion and at least one elongate portion configured to extend from the arcuate portion. The method may further comprise encircling at least a portion of an annulus of a heart valve with the arcuate portion and adjusting a size of at least one of the arcuate portion and the elongate portion so as to alter a shape of the portion of the annulus. The method also may include securing the at least one elongate portion to an exterior surface of the heart.
According to another aspect, a method of treating a heart valve comprises providing a device having an arcuate portion and at least one elongate member configured to extend from the arcuate portion. The method further extending the at least one elongate member from the arcuate portion. The method also may comprise securing the at least one elongate member to an exterior surface of the heart, wherein the at least one elongate member extends from the arcuate portion to the heart wall in substantially the same plane as the arcuate portion.
Yet another aspect includes a device for treating a heart valve comprising an arcuate portion configured to at least partly encircle an annulus of the heart valve and at least one elongate portion extending from the arcuate portion and configured to be secured to an exterior surface of a heart wall surrounding a heart chamber associated with the valve. At least one of the arcuate portion and the elongate portion is configured to be adjusted in size so as to alter a shape of at least a portion of the annulus.
In yet another aspect, a device for treating a heart valve comprises an arcuate portion configured to be positioned proximate an annulus of the heart valve and at least one elongate member extending from the arcuate portion and configured to be secured to an exterior surface of the heart wall. The at least one elongate member extends from the arcuate portion to the heart wall in substantially the same plane as the arcuate portion.
According to yet another aspect, the invention includes a device for treating a heart valve comprising at least one substantially elongate member configured to be implanted in a lumen of a coronary vessel so as to encircle at least a portion of an annulus of the heart valve and alter a shape of at least the portion of the annulus. The device may further comprise a shape change element associated with the elongate member and configured to impart a local shape change to a portion of the valve annulus at a location corresponding to the shape change element.
Yet another aspect includes a device for treating a heart valve comprising at least one substantially elongate member configured to be implanted in a lumen of a coronary vessel so as to encircle at least a portion of an annulus of the heart valve and alter a shape of at least the portion of the valve annulus. The shape of at least a portion of the elongate member may be configured to be adjustable so as to impart a local shape change to a portion of the valve annulus at a location corresponding to at least the adjustable portion.
Yet another aspect of the invention includes a method for treating a heart valve comprising providing at least one substantially elongate member and extending at least a portion of the elongate member within a heart wall surrounding a chamber of the heart associated with the heart valve so as to encircle at least a portion of the heart chamber. The method may further comprise securing the elongate member in place with respect to the heart and compressing at least a portion of a heart wall surrounding at least the portion of the heart chamber so as to move leaflets of the valve toward each other so as to assist the valve in closing during at least a portion of the cardiac cycle.
In yet another aspect, a method for treating a heart valve comprises providing at least one substantially elongate member and extending at least a portion of the elongate member within a lumen of a coronary sinus so as to encircle at least a portion of a heart chamber. The method further comprises securing the elongate member in place with respect to the heart via securement mechanisms and compressing at least a portion of a heart wall surrounding the portion of the heart chamber so as to move leaflets of the valve toward each other so as to assist the valve in closing during at least a portion of the cardiac cycle.
Yet another aspect of the invention includes a device for treating a heart valve comprising an elongate member having first and second oppositely disposed ends, with the elongate member being relatively rigid, a first anchoring member configured to be attached to the first end of the elongate member, and a second anchoring member configured to be attached to the second end of the elongate member. The first anchoring member may be configured to engage a first exterior surface of a wall of the heart and the second anchoring member may be configured to engage a second exterior surface of the wall of the heart to maintain a position of the elongate member transverse a heart chamber associated with the valve and substantially along a line of coaptation of the valve. The length of the elongate member may be such that the elongate member is capable of maintaining a substantially normal distance between trigones of the valve.
In yet another aspect, a method for treating a heart valve comprises providing a relatively rigid elongate member having first and second oppositely disposed ends, securing the first end of the elongate member to a first exterior heart wall surface, and securing the second end of the elongate member to a second exterior heart wall surface, the second exterior surface being located substantially opposite to the first exterior surface such that the elongate member extends substantially transverse a heart chamber associated with the valve and substantially along a line of coaptation of the valve. The method also may comprise maintaining a substantially normal distance between the trigones of the valve via the elongate member.
Yet another aspect of the invention includes a device for treating leakage of a heart valve comprising an expandable plug member having an external surface, with at least a portion of the plug member being configured to be positioned proximate leaflets of the heart valve. The device also may comprise a securement mechanism attached to the plug member and configured to secure the plug member with respect to the heart such that during at least a portion of the cardiac cycle, the leaflets abut the external surface of the plug member to restrict bloodflow through the valve.
According to another aspect, a device for treating leakage of a heart valve comprises a plug member having a piston-like configuration and an external surface being configured to abut free ends of leaflets of the valve to restrict bloodflow through the valve during at least the portion of the cardiac cycle. The device may further comprise a securement mechanism attached to the plug member and configured to secure the plug member with respect to the heart.
Yet another aspect of the invention includes a method of preventing leakage in a heart valve comprising providing an expandable plug member having an external surface, delivering the plug member to a heart chamber containing a valve, and positioning the plug member proximate leaflets of the valve such that the leaflets contact the external surface of the plug member during at least a portion of the cardiac cycle so as to restrict bloodflow through the valve.